Influence Of Atomic Disorder Research Articles

Effect of swap and antisite disorder on electronic, mechanical and thermodynamic properties of equiatomic all-d-metal Heusler alloy NiVTiZn

The influence of atomic disorder on electronic, mechanical and thermodynamic properties of equiatomic quaternary all-d metal Heusler alloy NiVTiZn is studied by employing the first-principles calculations. The ground state of NiVTiZn is confirmed to be α-type structure with ferromagnetic nature, the calculated spin down energy gap and equilibrium lattice constant is ∼0.7 eV and 6.048 Å, respectively. The half metallicity could be maintained when uniaxial strain ratio increases from −7.28 % to 9.59 % and when c/a ratio ranges from 0.92 to 1.06, showing a robust half metallicity against the strain effect and tetragonal distortion. Six types of atomic swap disorder and twelve types of atomic antisite disorder are proposed. The V(Ni) and V(Zn) antisite disorders as well as V-Ni and V-Zn swap disorders are the most favorable owing to their negative formation energies. The 100 % spin polarization is preserved in V(Ti), Ni-Zn and V-Ti disordered structures although the width of band gap suffers contraction. The spin polarization of Ni(V), Ni(Zn), V(Zn) and Zn(Ni) disordered structures is also larger than 80 %. In addition, the effect of various disorder on mechanical and thermodynamic properties is also studied in detail.

The computational design of zinc-blende half-metals and their nanostructures

The influence of atomic disorder and heterointerfaces with III–V semiconductors on theelectronic and magnetic properties of zinc-blende (ZB) CrAs is studied by ab initiocalculations based on density-functional theory. Antisite Cr spins are coupledantiferromagnetically with the Cr spins at the ordinary sites, while the ferromagneticcoupling between the Cr spins at the ordinary sites is robust against defect formation. Thedegree of spin polarization is not reduced significantly by the impurity bands formed in theminority spin energy gap. In the ZB CrAs/GaAs junction, relatively high spin polarizationis retained even at the interface in contrast to usual half-metal/semiconductorheterojunctions. Complete spin polarization is also preserved throughout ZB CrAs/GaAsmultilayers and it is insensitive to the substitutional disorder between Cr and Ga sites.

Electronic structure studies of CeRhSb with Rh substituted by Pd and Ni

We have investigated the influence of the valence of Ce ions on the gap formation in CeRhSb-type Kondo insulators. We present the $3d$ x-ray photoemission spectroscopy (XPS) spectra for CeRhSb, ${\mathrm{CeRh}}_{1\ensuremath{-}x}{\mathrm{Pd}}_{x}\mathrm{Sb},$ and ${\mathrm{CeRh}}_{1\ensuremath{-}x}{\mathrm{Ni}}_{x}\mathrm{Sb}$ compounds. From the experimental Ce $3d$ XPS spectra we extracted the spectral weight of the different ${3d}^{9}{f}^{0},$ ${3d}^{9}{f}^{1},$ and ${3d}^{9}{f}^{2}$ final states. We used the Doniach-\ifmmode \check{S}\else \v{S}\fi{}unji\ifmmode \acute{c}\else \'{c}\fi{} method to separate the overlapping peaks in the $3d$ XPS spectra. Analysis of the ${3d}^{9}{f}^{2}$ weight using Gunnarsson-Sch\"onhammer theory suggests a hybridization interaction $\ensuremath{\Delta}$ of about 150 meV for CeRhSb. The hybridization energy $\ensuremath{\Delta}$ obtained for CeNiSb and CePdSb is $\ensuremath{\sim}3$ times smaller than that of the Kondo insulating compound CeRhSb. Analysis of the ${3d}^{9}{f}^{0}$ component indicates a mixed valence of Ce in CeRhSb, and a stable configuration of Ce in the Ni or Pd alloys. The experimental results indicate the influence of atomic disorder on the magnetic behavior of CePdSb and CeNiSb.

The influence of radiation induced atomic disorder on the superconducting properties of nb 3sn

After high dose neutron or ion irradiation of Nb 3Sn several authors have observed a marked depression of T c , H c2 and J c . By a model calculation within the framework of the linear chain model it is shown that these effects might be explained by the decrease of the electronic density of states at the Fermi level, E F, due to radiation induced atomic disorder. The influence of atomic disorder on E F, T c, and on the intrinsic superconducting material parameters λ, ξ, κ, h c , H c2 is calculated numerically and the results are compared with experiments. The depression of the critical current density for doses φ > 2 × 10 18 n/cm 2 , in spite of a softening of the elastic properties of the flux line lattice after irradiation, is shown to be due to a drastic decrease of the elementary pinning forces.